Magnetic recording binder containing aminoalkylphosphonate salt

ABSTRACT

A magnetic recording medium is prepared by applying a magnetic coating composition onto a non-magnetic support and curing said composition, said coating composition containing ferromagnetic particles dispersed in a binder comprising a thermoplastic resin selected from the group consisting of polyurethanes and polyester wherein there is chemically bonded to said resin at least one aminoalkylphosphonate represented by the formula: ##STR1## wherein R 1  and R 2  are the same or different oxyalkyl radicals having from 2 to 12 carbon atoms, R 3  is an alkylene radical having from 1 to 12 carbon atoms, or an aralkylene radical having from 7 to 10 carbon atoms R 4  is an alkyl radical having from 1 to 12 carbon atoms, a cycloalkyl radical having from 5 to 12 carbon atoms, or an aryl radical having from 6 to 12 carbon atoms wherein the aryl radical may contain a halogen atom, a hydroxyl group, or an amino group, and M +  is a metal ion or an ammonium ion.

This is a divisional of co-pending application Ser. No. 08/238,296 filedon May 5, 1994.

BACKGROUND OF THE INVENTION

This invention relates to magnetic recording media such as tapes anddiscs which are obtained by applying a magnetic coating on anon-magnetic support.

General purpose magnetic tapes and discs are produced by coating apolyethylene terephthalate film with a magnetic material prepared bydispersing ferromagnetic particles about 1 micron long in a resinousbinder. The resinous binder plays a very important role in providingexcellent dispersibility, filling efficiency, and orientation ofmagnetic particles as well as imparting excellent durability, abrasionresistance, heat resistance and smoothness to the magnetic coating andadhesion thereof to the support.

Examples of resinous binders conventionally used include vinylchloride/vinyl acetate copolymers, vinyl chloride/vinyl acetate/vinylalcohol copolymers, vinyl chloride/vinylidene chloride copolymers,polyurethane resins, polyester resins, acrylonitrile/butadienecopolymers, nitrocellulose, cellulose acetate butyrate, epoxy resins,and acrylic resins. Of these resins, conventional polyurethane resinshave excellent toughness and abrasion resistance compared to otherresins but often are inferior in properties such as blocking resistance,heat resistance, and running stability. For these reasons, a mixedsystem of polyurethane resins with nitrocellulose or vinylchloride/vinyl acetate copolymers is often used. The durability, heatresistance, and adhesive properties of polyurethanes may be improved bycuring with a polyisocyanate at from about room temperature to about 40°C. or higher after the application and drying of the magnetic coatingcomposition.

A magnetic recording layer having highly improved strength and otherproperties employs a binder resin comprising both a vinyl chloridecopolymer (e.g., a vinyl chloride/vinyl acetate/maleic anhydridecopolymer) and a polyurethane resin. Japanese Patent Publication No.59-8127 teaches the incorporation of a polar group into one or both ofthe constituent resins to enhance the dispersibility of ferromagneticpowders in such a binder.

The durability and abrasion resistance of conventional resinous bindersare still insufficient for use in video tapes, computer tapes, andfloppy discs, all of which are required to have high performance andhigh reliability. Demand for high density and high quality recordingmedia is increasing while smoothness is still desired. As the requiredsmoothness increases, the running durability has suffered and resinousbinders with higher durability must be developed. To do so, it has beenproposed to introduce multifunctional components into the polyurethaneswhich are reactive with the polyisocyanate; trimethylolpropane anddiethanolamine exemplify such components. A serious drawback to thisapproach is that the dispersibility of the magnetic particles oftendecreases as the durability improves. The high recording density andhigh quality required for magnetic media have been supplied in recentyears by fine magnetic particles of metals and barium ferrite butdurability and dispersibility are still required of resinous binders forsuch particles.

A method for improving the dispersibility of the particles by theincorporation of metal sulfonate groups or metal salts of acidicphosphorus compounds is taught in Japanese Patent Publication Nos.57-3134 and 58-41564 and in Japanese Patent Publication (Kokai) No.61-48122. More recently, Yatsuka et al has taught in U.S. Pat. No.5,009,960 that the presence of such multifunctional components in theresin containing the metal sulfonate group or metal salt of an acidicphosphorus compound for the purpose of improving the durability of suchcoating still results in a lesser dispersibility. Yatsuka et al furthertaught that the incorporation of a bicyclic amide acetal into thepolyurethane resin will overcome the deficiencies of the prior art. Apreferred polyurethane contains, as a functional group, a metal salt ofan acidic phosphorus compound having the formula: ##STR2## wherein M isan alkali metal atom; R¹ is a hydrocarbon group of 3 to 10 carbon atoms,X is an ester forming functional group, R² is an alkyl group of 1 to 12carbon atoms, a cycloalkyl group of 6 to 12 carbon atoms, an aryl groupof 6 to 12 carbon atoms which may contain a halogen atom, a hydroxylgroup, an amino group, or an OM' group wherein M' is a metal atom.

SUMMARY OF THE INVENTION

In view of this, the present inventors have studied extensively with theobject of improving the dispersibility of magnetic particles in theresinous binder while maintaining the mechanical properties of thebinder in the coating. The present inventors have found that thebicyclic amide acetal group is not needed in a binder resinincorporating their particular phosphorus compound.

It is an object of their invention, therefore, to provide a resinousbinder for ferromagnetic particles which has excellent dispersiblilityof such particles but which may be free of bicyclic amide acetal groups.

It is another object of this invention to provide such a binder whichalso has a high glass transition temperature.

It is another object of their invention to provide a magnetic coatingcomposition which has excellent dispersiblility of ferromagneticparticles and is free of vinyl chloride polymers and copolymerscontaining polar groups.

It is another object of their invention to provide a magnetic recordingmedium having such a coating.

It is still another object of this invention to provide a novel ionicphosphonate.

These and other objects of the invention which will become apparent fromthe following description are achieved by a binder resin containing afunctional group having the formula: ##STR3## wherein R¹ and R² are thesame or different oxyalkylene radicals having from 2 to 12 carbon atoms,R³ is an alkylene radical having from 1 to 12 carbon atoms, or anaralkylene radical having from 7 to 10 carbon atoms, R⁴ is an alkylradical having from 1 to 12 carbon atoms, a cycloalkyl radical havingfrom 5 to 12 carbon atoms, or an aryl radical having from 6 to 12 carbonatoms wherein the aryl radical may contain a halogen atom, a hydroxylgroup, or an amino group, and M⁺ is a metal ion or ammonium ion.

DETAILED DESCRIPTION OF THE INVENTION

The binder resin of this invention is a polyurethane or a polyester. Themagnetic coating composition of this invention may contain either orboth of these and may further contain other binder resins such as thosementioned hereinabove.

The polyurethane resin of this invention is one having a weight averagemolecular weight of from 3000 to 150,000 obtained by the reaction of (A)a polyol having a molecular weight of from 300 to 5,000, (B) a chainextender having a molecular weight of less than 1000, and (C) apolyisocyanate. The polyurethane may be a segmented block or randomcopolymer comprising a hard segment and a soft segment. Theaminoalkylphosphonate group of Formula I may be present in either orboth of the segments.

The polyol (A) may be a polyesterdiol, a polyetherdiol, a polycarbonatediol, a polycaprolactone diol, or a mixture of two or all of them.

The carboxylic acid component of the polyesterdiol is exemplified byaromatic dicarboxylic acids such as terephthalic, isophthalic,orthophthalic or its anhydride, and 1,5-naphthalic acid; aromaticoxycarboxylic acids such as p-oxybenzoic acid p-(hydroxyethoxy)benzoicacid; aliphatic dicarboxylic acids such as succinic, adipic, azelaic,sebacic, and dodecanedioc acid; alicyclic dicarboxylic acids such ascyclohexanedicarboxylic acid, hydrogenated 2,6-naphthalenedicarboxylicacid and the like.

The glycol component of the polyesterdiol includes theN,N-bis(hydroxyalkyl)aminoalkyl phosphonates from which the functionalgroups of Formula I are derived. Other examples of the glycol componentinclude ethylene glycol, propylene glycol, 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol,diethylene glycol, dipropylene glycol, 2-methyl-1,3-propane diol;2-butyl-2-ethyl-1,3-propane diol; 2,2,4-trimethyl-1,3-pentanediol;cyclohexanedimethanol, ethylene oxide and propylene oxide adducts ofbisphenol A, ethylene oxide and propylene oxide adducts of hydrogenatedbisphenol A, polyethylene glycol, polypropylene glycol,polytetramethylene glycol, and the like. The polyesterdiols that may beused in this invention are further exemplified by the polycaprolactonediols obtained by the ring opening polymerization of lactones such ase-caprolactone. Union Carbide's Tone 0260 is a commercial example ofsuch a diol.

The polyesterdiol is produced by the conventional procedure in which theacid and hydroxyl group containing compound are heated in the presenceof an acid catalyst until the acid number is reduced to about 10 orless.

The polyetherdiols are exemplified by the polyethylene glycols,polypropylene glycols, polytetramethylene glycols, and mixedpoly(propylene/ethylene) glycols, particularly those having up to about20% by weight of ethylene oxide units. All of said polyetherdiols arecommercially available.

Polycarbonate diols are exemplified by those offered by PPG Industries,Inc., under the Duracarb trademark as the 120 series and the 140 series.

The ionic phosphonates, in particular, theN,N-bis(hydroxyalkyl)aminoalkyl phosphonates from which the functionalgroups of Formula I are derived, are made by a modified Mannich reactionof a dialkyl hydrogen phosphite with an N-N-bis-hydroxyalkylamine orhydroxyaralkylamine and an aldehyde, followed by the saponification ofone of the phosphonate ester groups by a base. M⁺ is exemplified by thesodium, potassium, lithium, ammonium, alkylammonium and quaternaryammonium ions in salts of N,N-bis-(2-hydroxyethyl)aminomethylphosphonate, N,N-bis-(3-hydroxypropyl) aminomethyl phosphonate,N,N-bis-(4-hydroxybutyl)aminomethyl phosphonate,N,N-bis-(4-hydroxybutyl)aminoethyl phosphonate, N-(2-hydroxyethyl),N-(3-hydroxypropyl)!aminoethyl phosphonate, and N-(2-hydroxyethyl),N-(3-hydroxypropyl)!aminomethyl phosphonate.

Trifunctional components such as trimellitic anhydride,trimethylolpropane, glycerin, and the like may be used in combinationwith the difunctional acids and glycols; but care must be taken in theformulation of binder resins for magnetic media to preserve goodperformance thereof.

Thus, the polyurethane resin of this invention may have a polyester,polyether or polycarbonate backbone or a combination thereof. The chainextender (B) has the effect of regulating the urethane group content ofthe polyurethane resin to impart toughness to the resin. Examples of thechain extender include straight chain glycols such as ethylene glycol;1,3-propylene glycol; 2-methyl-1,3-propane diol;2-butyl-2-ethyl-1,3-propane diol; 1,4-tetramethylene glycol;1,6-hexanediol, cyclohexanedimethanol, xylylene glycol, diethyleneglycol; triethylene glycol; and an ethylene oxide adduct of bisphenol A;branched chain glycols such as propylene glycol; neopentyl glycol;1,2-butanediol; 1,3-butanediol; 2,2,4-trimethyl-1,3-pentanediol; and apropylene oxide adduct of bisphenol A; water; aminoalcohols such asmonoethanolamine and N-methylethanolamine; diamines such as ethylenediamine, hexamethylene diamine, and isophorone diamine are suitable insome instances, but to avoid crosslinking, secondary diamines such asN,N'-dialkyl phenylenediamine; p,p'-di(alkylamino)diphenylmethane;piperazine and the like are preferred. The amount of chain extender isdetermined in part by the size and nature of the chain extender and inpart by the desired properties. Trifunctional chain extenders such astrimethylolpropane, diethanolamine, triethanolamine, and glycerin mayalso be used with care as to their effect on the performancecharacteristics of the polyurethane.

Polyisocyanate (C) is exemplified by 2,4-tolylene diisocyanate;2,6-tolylenediisocyanate; p-phenylenediisocyanate;diphenylmethanediisocyanate or MDI; m-phenylene diisocyanate;hexamethylenediisocyanate; tetramethylenediisoacyanate;3,3'dimethoxy-4,4'-biphenylenediisocyanate; 2,4-naphthalenediisocyanate;3,3'-dimethyl-4,4'-biphenylenediisocyanate;4,4'diphenylenediisocyanate; 4,4'-diisocyanate-diphenyl ether,1,5-naphthalenediisocyanate; p-xylylenediisocyanate; m-xylylenediisocyanate; 1,3-diisocyanatomethylcyclohexane;1,4-diisocyanatomethylcyclohexane; 4,4'-diisocyanatodicyclohexane;4,4'-diisocyanatodicyclohexylmethane; isophorone diisocyanate; and thelike. Triisocyanates, such as 2,4-tolylenediisocyanate trimer andhexamethylenediisocyanate trimer and the like, are also used with careas to their effect on the performance characteristics of thepolyurethane.

In producing the polyurethane resin used in the present invention, themolar ratio of the isocyanate to hydroxyl is in the range of 1:2 to 1:1.Said ratio is a factor in determining the molecular weight of the resin.When the isocyanate content is too large, the resulting polyurethane isisocyanate-terminated and has a poor storage life. When the hydroxylcontent is too large, the molecular weight decreases. A preferred rangefor the ratio of NCO/OH equivalents is from 1:1 to 1:1.2. A preferredweight average molecular weight range for the polyurethane resin is from3000 to 150,000. When it is less than 3000, the mechanical strength ofthe polyurethane suffers; when it exceeds 150,000, the solutionviscosity makes handling increasingly difficult.

The polyaddition reaction for producing the polyurethane of thisinvention may be of the one-shot procedure wherein all of the componentsare reacted at one time, or of the prepolymer method wherein a longchain diol is first reacted with excess isocyanate and the resultingisocyanate-terminated prepolymer is polymerized using a chain extender.The reaction may be carried out in either the molten state or insolution. The temperature is suitably about 120° C. and the time isgenerally about 90 minutes. The block polymer method is a variation onthe prepolymer method wherein another long chain hydroxyl groupcontaining compound is reacted with the isocyanate-terminatedprepolymer. Stannous octoate, stannous oxalate, dibutyltin dilaurate,triethylamine, and the like may be used as a catalyst. Ultraviolet lightabsorbers, hydrolysis inhibitors, antioxidants, and other usefuladditives may be added before, during, or after the production of thepolyurethane.

The polyester resin used as a binder resin in the magnetic coatingcomposition of this invention may be like the polyesterdiol (A) exceptthat its weight average molecular weight is from 3000 to 150,000.

The polyol (A) used in the preparation of the polyurethane resin of thisinvention and the polyester resin which is, itself, used as a binderresin in this invention both contain a sufficient amount of theaminoalkyl phosphonate salt which furnishes the functional group ofFormula I to yield a binder having a phosphonate salt concentration offrom about 5 to about 1000 gram equivalents per 1×10⁶ grams of polymer.

The ferromagnetic particles used in the coating composition of thepresent invention include magnetic metal powders such as iron, metaloxides such as γ-Fe₂ O₃, γ-Fe₂ O₃ /Fe₃ O₄ mixed crystal, CrO₂, andcobalt-containing iron oxide; ferromagnetic alloy powders such as Fe--Coand Fe--Co--Ni; and barium ferrite. A suitable magnetic particle/binderratio is about 3.5:1 by weight. Pigments such as carbon black, andabrasives such as alumina, green chrome, and α-Fe₂ O₃ may also bepresent in the coating composition. The particle size of each is from0.01 to 2μ.

A solvent is generally used in the production of a magnetic coatingcomposition of this invention. Ketones such as methyl ethyl ketone,methyl isobutyl ketone, and cyclohexanone; esters such as methylacetate, ethyl acetate, and ethyl butyrate; glycol ethers such asethylene glycol monoethyl ether; toluene, xylene; tetrahydrofuran, andmixtures of two or more of the preceding solvents are examples of thosethat are useful.

Plasticizers, lubricants, dispersing agents, antistatic agents and otheradditives may be added to the magnetic coating composition. Dibutylphthalate and triphenyl phosphate exemplify the plasticizers.Dioctyl-sulfosodium succinate, t-butylphenol polyethylene ether, sodiumethylnaphthalenesulfonate, dilauryl sulfate, zinc stearate, soybean oillecithin, myristic acid, butyl myristate and silicone oil exemplify thelubricants, antistatic agents, and dispersing agents.

The magnetic recording medium of this invention comprises a non-magneticsupport and a magnetic coating formed thereon by applying the magneticcoating composition containing magnetic particles dispersed in thebinder described above to the support and drying it. Material for thesupport includes polyesters, polypropylene, cellulose triacetate,polycarbonate, poly(vinylchloride), and aluminum. Examples of suitablefilms of polyethylene terephthalate are described in U.S. Pat. Nos.4,454,312; 4,595,715; and 4,693,932, all of which are incorporatedherein by reference.

Among the devices for dispersing the components of the magnetic coatingcomposition there may be mentioned a ball mill, pebble mill, sand milland high speed stone mill.

Methods for coating are exemplified by the knife coating, wire barcoating, doctor blade coating, reverse roll coating, and calendercoating, and gravure methods. After the magnetic coating has been coatedonto the non-magnetic support surface, the coated film is generallysubjected before drying to an orienting treatment in a magnetic fieldand to a smoothing treatment. The magnetic coating layer is from about 1micron to about 12 microns thick and provides a magnetic field of fromabout 600 to 5000 gauss.

The binder resin of the present invention becomes a uniform resinsuperior in dispersibility of magnetic particles by virtue of theincorporation of the aminoalkyl phosphonate salt described herein. As aresult, the magnetic recording medium of this invention, the binder ofwhich includes at least one of the aminoalkyl phosphonate modifiedresins of this invention, is superior in the filling characteristics andorientation of the magnetic particles and the smoothness of the magneticlayer of the recording medium.

The binder resins and magnetic coating compositions of this inventionare illustrated specifically in the following examples wherein all partsare parts by weight unless otherwise indicated. Magnetic recording mediaof this invention are made by adding a cross-linking agent such as atrifunctional polyisocyanate to the magnetic coating composition,placing it on a support tape, drying it, and curing it in a conventionalmanner.

The invention is illustrated more specifically by the following exampleswherein all parts are by weight unless otherwise indicated. Allviscosities were measured by the Brookfield method with a #2 spindle at20 rpm and 25° C. unless otherwise indicated. Gloss was measured at anangle of 60°.

EXAMPLE 1 Monosodium ethyl-N,N-bis(hydroxyethyl)aminomethyl phosphonate

This intermediate was prepared by adding 256 parts ofdiethyl-N,N-bis(hydroxyethyl)aminomethyl phosphonate to a 14% by weightsolution of sodium hydroxide in water in a stirred reactor equipped witha distillation column and heating the mixture slowly to causedistillation of by-product ethanol to begin. The column temperature wasmaintained at 72°-75° C. and the reactor temperature was maintained at80° C. until distillation stopped. The pH of the cooled product was 10.1and the percent solids was 51.7.

EXAMPLE 2

Alternatively, the sodium ethyl-N,N-bis (hydroxyethyl)aminomethylphosphonate (hereinafter called HAP) was made by heating a mixture of849.5 parts of cyclohexanedimethanol (CHDM), 129.2 parts of deionizedwater, and 448.2 parts of the diethyl phosphonate of Example 1 in areactor fitted with a condensation collecting column, a thermometer, andan addition funnel to 60°-65° C. and adding 167.8 parts of a 42.6% byweight solution of NaOH at a rate of about 60-80 drops/minute. Thetemperature was thus maintained in the 70°-75° C. range over a period of50 minutes. Shortly after the completion of the NaOH addition, thetemperature dropped to 72° C. The by-product ethanol and the solventwater were removed by distillation to give a mixture containing CHDM and36% by weight of the phosphonate of this invention.

EXAMPLE 3

A first polyester having an OH number of 205 and made by the reaction of42.5 parts of CHDM, 20.2 parts of 2-butyl-2-ethyl-1,3-propane diol(BEPD), and 37.2 parts of adipic acid was blended with a secondpolyester having an OH number of 195 and made from 42.1 parts of CHDM,20.0 parts of BEPD, and 37.9 parts of adipic acid. The OH number of theresulting blend of "hard" polyesters was 198. Two "soft" polyesters werealso mixed to give a second blend having an OH number of 198. The first"soft" polyester had an OH number of 195 and was made from 30 parts ofbutanediol (BD), 23 parts of BEPD, and 47 parts of adipic acid. Thesecond "soft" polyester had an OH number of 205 and was made from 30.3parts of BD, 23.1 parts of BEPD, and 46.6 parts of adipic acid. A 50% byweight solution of HAP in ethylene glycol was mixed,in turn, with a70/30 mixture of the "hard" and "soft" blends to extend the OH number to250. The weight percentages of each component were: 66.09% of the hardpolyester, 28.32 of the soft polyester, and 5.59% of the glycol solutionof the phosphonate of this invention. Seven hundred parts of thismixture and 379.2 parts of diphenylmethane-4,4'-diisocyanate (MDI) weremixed and reacted at 120° C. for 90 minutes to give a polyurethane ofthis invention. A 15% by weight solution of this polyurethane in methylethyl ketone had a viscosity of 188 cps.

EXAMPLE 4 Preparation of Polyester Containing HAP

The general procedure of Example 2 was followed to make a mixture of HAPand CHDM except that 566.3 parts (3.9 moles) of molten CHDM, 298.8 parts(1.2 moles) of the phosphonate, 86.0 parts of water, and 111.9 parts ofthe NaOH solution were used, 10.0 parts of Irganox 1076 inhibitor wereadded, and a nitrogen purge was used to help the removal of ethanol andwater. Then, an additional 1249.3 parts of CHDM were added and thetemperature was raised to 80°-90° C. whereupon 1169.2 parts (8.0 moles)of adipic acid were added. Heating was continued using an oil bathtaking care that the maximum temperature differential between the bathand the reaction mixture was 35° C. As soon as distillation began, thenitrogen purging was stopped and the reaction mixture was heated to amaximum of 195°-200° C. where it was held for five hours. The pressurewas then reduced to about 45-50 mm Hg and the reaction mixture was heldfor one hour at 195°-200° C. The column temperature was held at 50° C.The condensation was completed by adding 0.25 part of stannous oxalateand reducing the pressure still further to 20-25 mm Hg while holding thetemperature at 195°-200° C. until the acid number was less than 1. TheOH number of the product was 187.9.

The procedure was repeated except that the second charge of CHDM was 9.7moles. The acid number was 0.78 and the OH number was 214.1.

Preparation of Polyurethane/polyurea

A blend of the polyesters having the OH values of 187.9 and 214.1 wasmade to achieve an OH value of 198. A portion (38.9 parts) of the blendwas then mixed with two other polyesters having an OH value of 198: aCHDM/MP Diol/Adipic acid polyester (155.5 parts) and an MP Diol/Adipicacid polyester (194.4 parts). MP Diol is 2-methyl-1,3-propane diol. Tothis blend there was added 78 parts of N, N'-dibutyl phenylenediamineand the mixture was reacted with 252.2 parts of MDI. The viscosity of a15% by weight solution of it in methyl ethyl ketone (MEK) was 20 cps anda 15% by weight solution in a MEK/cyclohexanone(CHO)/toluene mixture(1:1:1)_(w) had a viscosity of 32 cps.

EXAMPLE 5

The blend of phosphonated polyesters of Example 4 was combined with theMP Diol/Adipic acid polyester of that example in a 15:85 weight ratioand MP Diol was added as a chain extender. The amounts of each componentwere 199.5, 1130.9, and 69.6 parts, respectively. To this mixture therewas added 759.3 parts of MDI and the reaction was carried out in 90minutes. A 15% solution of the polyurethane in MEK had a viscosity of 24cps and at 20% solids, the viscosity was 62 cps. A 15% solution of thepolyurethane in a MEK/CHO/toluene mixture (1:1:1)_(w) had a viscosity of40 cps.

EXAMPLE 6

The general procedure of Example 5 was followed except that the amountof MDI was reduced to 754.4 parts. The viscosities of the solutions were34 cps, 100 cps, and 58 cps, respectively.

EXAMPLES 7 & 8 Magnetic Coating Compositions

A Binder Solution containing 181 parts of the sodio-sulfo copolymer ofvinyl chloride, vinyl alcohol, and vinyl acetate sold under thetrademark Zeon MR-110 by Nippon Zeon, in a solvent consisting of 341.8parts each of MEK, CHO, and toluene was prepared for use in the millbasehaving the formulation shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        COMPONENT             WEIGHT                                                  ______________________________________                                        Cobalt-modified iron oxide (Auvico AX                                                               1900.0                                                  2000)                                                                         Carbon black (Mogul L)                                                                              152.0                                                   Aluminum oxide (Norton)                                                                             38.0                                                    Methyl ethyl ketone   635.8                                                   Cyclohexanone         496.1                                                   Toluene               635.8                                                   Myristic acid         14.3                                                    Binder Solution (15% total solids)                                                                  1206.4                                                  ______________________________________                                    

A KDL pilot mill was used to mill the millbase formulation. Beforemilling the Brookfield viscosity was 5500 using a #6 spindle at 20 rpm.After milling, it was 12600.

Polyurethane Solutions A and B containing 271.4 parts of the product ofExample 5 and the product of Example 6, respectively, were prepared in asolvent consisting of 512.7 parts each of MEK, CHO, and toluene for usein the formulation of letdowns for making the magnetic coatingcompositions of Examples 7 and 8 as follows:

To each of said Polyurethane Solutions, there were added 109.4 parts ofMEK, 20.5 parts of CHO, 109.4 parts of toluene, and 14.25 parts of butylmyristate to make Letdown Solutions C and D.

The magnetic coating compositions of Examples 7 and 8 were made byletting down the millbase with Letdown Solutions C and D, respectively,using a letdown factor of 40.63 parts per 100 parts of millbase.

EXAMPLE 9 and Comparative Example 1

A millbase binder of this invention was prepared as follows:

To 566.3 parts (3.9 moles) of molten CHDM there were added 608.3 partsof the solution of the sodium phosphonate of Example I, 0.25 part ofstannous oxalate catalyst, and 1169.2 parts of adipic acid. Thetemperature was held at 195°-200° C. until the distillation of waterstopped. Then, after cooling the reaction mixture to 140°-150° C., anadditional 1249.3 parts of CHDM were added and the temperature wasraised to 195°-200° C. again. When the distillation stopped again, thepressure was reduced to 45-50 mm Hg and the reaction was continued forone hour at the same temperature while maintaining the columntemperature at 50° C. to minimize loss of CHDM. A second charge of 0.5part of the catalyst was then added, the pressure was reduced to 20-25mm Hg and the reaction was completed at 195-200 as indicated by an acidnumber of about one. The OH number was 189.6.

Preparation of a polyurethane of this invention

A first polyester having an OH number of 205 made from a reactionmixture composed of, by weight, 42.5% CHDM, 20.2% BEPD, and 37.2% adipicacid and a second polyester having an OH number of 195 made from areaction mixture having the same components but in the ratio42.1:20.0:37.9 were mixed to obtain a blend having an OH number of 198.A mixture of 868.8 parts of the phosphonated polyester described above,372.4 parts of said polyester blend, and 158.8 parts of BEPD was reactedwith 738.1 parts of MDI to form a polyurethane of this invention.Molecular weight determinations showed the product to have a MW_(w) of18,800; a MW_(n) of 7200, and a MW_(z) of 32,000. The viscosity of a 15%solution in MEK was 420 cps. At the same concentration inMEK/CHO/toluene (1:1:1)_(w), the viscosity was 142 cps.

Comparative Example 1

A binder of the prior art, the sodio- sulfocopolymer of vinyl chloride,vinyl alcohol, and vinyl acetate sold under the trademark Zeon MR-110 byNippon Zeon.

Binder Solutions

A solution of the above-described polyurethane of this invention and asolution of the binder of Comparative Example 1 were each prepared bydissolving 95.4 parts of the binder in a solvent mixture containing179.9 parts each of MEK, CHO, and toluene.

Millbase Constructions

The binder solutions were used in the millbase formulations shown inTable 2.

                  TABLE 2                                                         ______________________________________                                        COMPONENT             WEIGHT                                                  ______________________________________                                        Cobalt-modified iron oxide (Auvico AX                                                               1000.0                                                  2000)                                                                         Carbon black (Mogul L)                                                                              80.0                                                    Aluminum oxide (Norton)                                                                             20.0                                                    Methyl ethyl ketone   334.6                                                   Cyclohexanone         261.1                                                   Toluene               334.6                                                   Myristic acid         7.5                                                     Binder Solution (15% Solids)                                                                        634.9                                                   ______________________________________                                    

The Brookfield viscosity of the millbase formulation of Example 9 beforebeing milled was 4100 cps using a #6 spindle at 20 rpm and 74° F. Aftermilling in a KDL pilot mill, it was 8750 cps.

The Brookfield viscosity of the millbase formulation of ComparativeExample 1 before being milled was 4950 cps using a #6 spindle at 20 rpm.After milling in a KDL pilot mill, it was 7550 cps.

The dispersive power (expressed in terms of gloss), coercivity (Hc),squareness ratio (SR), and switching field distribution (SFD) of themillbase of Example 9 after five passes through a sand mill are shown inTable 3.

                  TABLE 3                                                         ______________________________________                                        Pass   MB        Gloss  Hc       SR   SFD                                     ______________________________________                                        1      9         53     740      0.79 0.42                                           CE1       51     739      0.77 0.44                                    2      9         91     747      0.81 0.41                                           CEI       88     749      0.81 0.40                                    3      9         103    748      0.82 0.40                                           CE1       92     743      0.81 0.40                                    4      9         108    746      0.81 0.40                                           CE1       96     741      0.81 0.40                                    5      9         110    748      0.82 0.40                                           CE1       99     740      0.81 0.40                                    ______________________________________                                    

EXAMPLE 10

To 566.3 parts (3.9 moles) of molten CHDM there were added 608.3 partsof the solution of the sodium phosphonate of Example I, 0.25 part ofstannous oxalate catalyst, and 1169.2 parts of adipic acid. Thetemperature was held at 195°-200° C. until the distillation of waterstopped. Then, after cooling the reaction mixture to 140°-150° C., anadditional 1249.3 parts of CHDM were added and the temperature wasraised to 195°-200° C. again. When the distillation stopped again, thepressure was reduced to 45-50 mm Hg and the reaction was continued forone hour at the same temperature while maintaining the columntemperature at 50° C. to minimize loss of CHDM. A second charge of 0.5part of the catalyst was then added, the pressure was reduced to 20-25mm Hg and the reaction was completed at 195-200 as indicated by an acidnumber of about one. The OH number was 189.6.

Preparation of polyurethane

A mixture of 620.6 parts of the phosphonated polyester thus made, 620.6parts of a polyester of MP Diol/adipic acid having an OH number of194.7, and 158.9 parts of BEPD was reacted with 758.4 parts of MDI toform a polyurethane of this invention. A determination of its molecularweight gave a MW_(w) of 20,431, a MW_(n) of 8888, and a MW_(z) of33,351. The viscosity of a 15% solution in MEK was 25 cps. At the sameconcentration in MEK/CHO/toluene (1:1:1)_(w), the viscosity was 44 cps.

EXAMPLE 11

A first polyester having an OH number of 195 and made from a reactionmixture composed of 30% by weight of butanediol, 23% of BEPD, and 47% ofadipic acid was blended with a second polyester having an OH number of205 made from a reaction mixture composed of 30.3% of butanediol, 23.1%of BEPD, and 46.6% of adipic acid to give a polyester blend having an OHnumber of 198.

A mixture of 625.8 parts of the blend and 625.8 parts of thephosphonated polyester described in Example 10, and 154.8 parts of BEPDwas reacted with 758.5 parts of MDI to give another polyurethane of thisinvention. A determination of its molecular weight gave a MW_(w) of21,691, a MW_(n) of 7563, and a MW_(z) of 38,123. The viscosity of a 15%solution in MEK was 1200 cps. At the same concentration in the 1:1:1solvent, the viscosity was 162 cps.

Comparative Example 2

This is a binder of the prior art, Morthane CA-398 polyurethane, sold byMorton International, Inc. It is free of functional groups and itsweight average molecular weight is 73,800 and the number averagemolecular weight is 29,500.

EXAMPLES 12-16

Letdown solutions of the binders of Examples 10 and 11 and ComparativeExample 2 were made according to the following formulation:

    ______________________________________                                                MEK   327.4                                                                   CHO   280.6                                                                   TOL   327.4                                                                   BuMyr*                                                                              7.5                                                                     Binder                                                                              142.9                                                                         1085.8                                                          ______________________________________                                         *BuMyr = butyl myristate                                                 

The millbases of Example 9 and Comparative Example 1 were each letdownwith 40.6 parts of these solutions per 100 parts of millbase. Themagnetic oxide:binder ratio was 3.50:1. The letdown compositions weredeposited on strips of 36 μm thick polyethylene terephthalate film sothat the coating was 4 μm thick after drying. The compositions of thisinvention and of the prior art are identified as follows:

    ______________________________________                                        12        millbase of Comp. Ex. 1 + Letdown of Ex. 10                         13        millbase of Ex. 9 + Letdown of Ex. 10                               14        millbase of Ex. 9 + Letdown of Comp. Ex. 2                          15        millbase of Comp. Ex. 1 + Letdown of Ex. 11                         16        millbase of Ex. 9 + Letdown of Ex. 11                               ______________________________________                                    

The properties of said compositions are shown in Table 4, wherein theviscosities are shown as V Im (immediate) and V Ov (overnight), thedispersive power of the binder is expressed in terms of gloss,coercivity is H_(c), squareness ratio is SR, and switching fielddistribution is SFD. Coercivity is the amount of externally appliedmagnetic strength necessary to reduce the magnetism of the ferromagneticparticles to zero. Squareness ratio is the ratio of residual magneticflux to saturated magnetic flux. The switching field distribution is ameasure of the population of particles that switch polarities at a givenmagnetic strength. The viscosities were taken with a #4 spindle at 50rpm at room temperature.

                  TABLE 4                                                         ______________________________________                                        Ex.     Gloss  Hc       SR   SFD    V Im V Ov                                 ______________________________________                                        12      106    741      0.81 0.41    892  932                                 13      110    750      0.80 0.41    944  980                                 14       90    752      0.78 0.42   1350 1740                                 15      102    742      0.81 0.41   1480 1550                                 16      106    749      0.79 0.42   1700 1640                                 ______________________________________                                    

Millbases of this invention containing ferromagnetic metal particleswere prepared as follows:

EXAMPLE 17

To 566.3 parts (3.9 moles) of molten CHDM there were added 608.3 partsof the solution of the sodium phosphonate of Example 1, 0.25 part ofstannous oxalate catalyst, and 1169.2 parts of adipic acid. Thetemperature was held at 195°-200° C. until the distillation of waterstopped. Then, after cooling the reaction mixture to 140°-150° C., anadditional 1249.3 parts of CHDM were added and the temperature wasraised to 195°-200° C. again. When the distillation stopped again, thepressure was reduced to 45-50 mm Hg and the reaction was continued forone hour at the same temperature while maintaining the columntemperature at 50° C. to minimize loss of CHDM. A second charge of 0.5part of the catalyst was then added, the pressure was reduced to 20-25mm Hg and the reaction was completed at 195-200 as indicated by an acidnumber of 0.99. The OH number was 187.9

A second phosphonate containing polyester was made according to the samegeneral procedure except that 1393.5 parts of CHDM made up the secondcharge. The acid number was 0.78 and the OH number was 214.1.

A blend containing 61.4 percent the first of these phosphonatedpolyesters and 38.6 percent the second was made to obtain a polyesterhaving an OH number of 198.

Preparation of a polyurethane of this invention

A mixture of 665.3 parts of the phosphonated polyester blend, 665.3parts of polyester made from 2-methyl-1,3-propanediol and adipic acidand having an OH number of 198, and 69.6 parts of2-methyl-1,3-propanediol was reacted with 763.3 parts of MDI for 95minutes to give a polyurethane of this invention. A 15% by weightsolution of the polyurethane in a solvent containing equal weights ofMEK, CHO, and toluene had a viscosity of 270.

Comparative Example 3

The binder used for comparative purposes was the Zeon MR-110 vinylchloride/vinyl acetate/vinyl alcohol copolymer.

Binder Solutions

Solutions of the above-described polyurethane binder of this invention,of Example 9, and of the vinyl binder of the prior art were prepared bydissolving 150.0 parts of the binder in a solvent mixture containing 340parts each of MEK and tetrahydrofuran, and 170 parts of toluene.

Millbase Constructions

The binder solutions were used in the millbase formulation shown inTable 5.

                  TABLE 5                                                         ______________________________________                                        COMPONENT        WEIGHT                                                       ______________________________________                                        Kanto Denka P1100B                                                                             1000.0                                                       iron                                                                          Carbon black     20.0                                                         (Regal 500 R)                                                                 Aluminum oxide   60.0                                                         (Norton)                                                                      Methyl ethyl ketone                                                                            486.7                                                        THF              486.7                                                        Toluene          243.3                                                        stearic acid     10.0                                                         Binder Solution  1000.0                                                       ______________________________________                                    

The millbase concentrates were coated onto strips of 36 μm thickpolyethylene terephthalate film so that the coating was 4 μm thick afterdrying so that the dispersive power, coercivity, squareness ratio, andswitching field distribution of the millbases of Example 17, Example 9,and Comparative Example 3 after each of several passes through a sandmill could be measured. The results are shown in Table 6.

                  TABLE 6                                                         ______________________________________                                        Pass   MB         Gloss  Hc      SR   SFD                                     ______________________________________                                        1      Ex 9       98     1604    0.858                                                                              0.511                                          Ex 17      86     1613    0.811                                                                              0.512                                          C.E. 3     52     1604    0.813                                                                              0.524                                   2      Ex 9       114    1590    0.828                                                                              0.501                                          Ex 17      97     1619    0.830                                                                              0.504                                          C.E. 3     58     1595    0.753                                                                              0.549                                   3      Ex 9       118    1601    0.868                                                                              0.499                                          Ex 17      99     1615    0.843                                                                              0.508                                          C.E. 3     74     1583    0.779                                                                              0.542                                   4      Ex 9       118    1606    0.868                                                                              0.501                                          Ex 17      100    1615    0.853                                                                              0.511                                          C.E. 3     75     1582    0.783                                                                              0.548                                   4 +    Ex 9       117    1592    0.835                                                                              0.523                                   1 hr   Ex 17      93     1608    0.806                                                                              0.549                                          C.E. 3     53     1577    0.752                                                                              0.593                                   ______________________________________                                    

EXAMPLES 18-21

A series of ionic phosphonate-containing polyurethanes were made by thereaction of MDI with mixtures of MPD (2-methyl-1,3-propanediol) or BEPD(2-butyl-2-ethyl-1,3-propanediol), the phosphonated polyester blend(PPB), and the MPD/Adipic acid polyester (MPDA) of Example 17 whereinthe weight ratio of PPB to the MPDA varied from 7:93 to 40:60. The partsby weight of the chain extenders, each polyester and of the MDI aregiven in Table 7 along with the viscosity of a 15% by weight solution ofeach polyurethane in an MEK/CHO/toluene (1:1:1)_(wt) solvent mixture andthe viscosity of such a solution of the polyurethane of ComparativeExample 2.

                  TABLE 7                                                         ______________________________________                                        Ex No. PPB    MPDA      MPD  BEPD   MDI  Viscosity                            ______________________________________                                        18      93.1  1237.3    69.6 --     760.4                                                                              40 cps                               19     188.3  1066.7    --   145.0  761.3                                                                              48 cps                               20     399.1   931.3    69.6 --     753.2                                                                              58 cps                               21     532.1   798.3    69.6 --     750.2                                                                              88 cps                               CE 2   --     --        --   --     --   148 cps                              ______________________________________                                    

Millbase Comparison

Binder Solutions were made from 215.9 parts each of MEK, CHO, andtoluene (TOL), and 114.3 parts of the binders of Examples 20 and 21 forthe purpose of preparing millbase constructions according to thefollowing formulation:

                  TABLE 8                                                         ______________________________________                                        COMPONENT             WEIGHT                                                  ______________________________________                                        Cobalt-modified iron oxide (Auvico AX                                                               1200.0                                                  2000)                                                                         Carbon black (Mogul L)                                                                              96.0                                                    Aluminum oxide (Norton)                                                                             24.0                                                    Methyl ethyl ketone   401.5                                                   Cyclohexanone         313.3                                                   Toluene               401.5                                                   Myristic acid         9.0                                                     Binder Solution       761.9                                                   ______________________________________                                    

The Brookfield viscosity of the millbase of Example 20 before millingwas 4550 cps and after six passes it was 12,900 cps (both with #6spindle at 20 rpm).

The Brookfield viscosity of the millbase of Example 21 before millingwas 2950 cps and after six passes it was 15,500 cps (both with #6spindle at 20 rpm).

Each of the millbase solutions were passed through a KDL pilot millseveral times and after each pass a sample was coated onto 36 μm thickpolyethylene terephthalate film so that the dried coating was 4 μmthick.

The dispersive capacity, coercivity, squareness ratio, and switchingfield distribution of the coating on the film after each pass are givenin Table 9.

                  TABLE 9                                                         ______________________________________                                        Pass   MB         Gloss  HC      SR   SFD                                     ______________________________________                                        1      20         46     749     0.762                                                                              0.486                                          21         40     743     0.762                                                                              0.491                                   2      20         87     757     0.803                                                                              0.447                                          21         87     758     0.807                                                                              0.450                                   3      20         92     749     0.791                                                                              0.451                                          21         95     758     0.808                                                                              0.447                                   4      20         97     754     0.811                                                                              0.448                                          21         102    759     0.817                                                                              0.441                                   5      20         101    752     0.816                                                                              0.445                                          21         104    754     0.817                                                                              0.436                                   6      20         102    754     0.806                                                                              0.445                                          21         106    755     0.818                                                                              0.439                                   6 +    20         94     729     0.746                                                                              0.508                                   24 hr  21         97     741     0.752                                                                              0.501                                   ______________________________________                                    

EXAMPLES 22-25 and Comparative Example 4 Magnetic Recording Compositions

Letdown Constructions of each of the binders of Examples 18-21 were madeby first dissolving 171.4 parts of the binder in a solvent made up of323.8 parts each of MEK, CHO, and TOL and then diluting each solution bymixing 1142.9 parts of it with a solution made up of 69.1 parts of MEK,13 parts of CHO, 69.1 parts of toluene, and 9 parts of butyl myristate.A millbase construction was prepared from the MR-110 binder according tothe formula given in Table 8 above.

Magnetic recording compositions (MRC) of Examples 22-25 and ofComparative Example 4 prepared according to the formulation shown inTable 10 were coated onto strips of 36μ thick polyethylene terphthalatefilm so that the coating was 4μ thick after drying. The gloss andviscosity of the MRC's initially and after the period shown are given inTable 11. In like manner,the coercivity (H_(c)), squareness ratio (SR),and switching field distribution (SFD) are given in Table 12.

                  TABLE 10                                                        ______________________________________                                        Ex No.                                                                              Millbase LDC 18  LDC 19 LDC 20                                                                              LDC 21                                                                              LDC CE2                             ______________________________________                                        22    403.5    163.9   --     --    --    --                                  23    401.0    --      162.9  --    --    --                                  24    400.8    --      --     162.9 --    --                                  25    400.9    --      --     --    162.9 --                                  CE 4  400.5    --      --     --    --    162.7                               ______________________________________                                         LCD = letdown construction                                               

                  TABLE 11                                                        ______________________________________                                                  Viscosity                                                                     Init     30 min     24 hrs                                          Gloss       #6 @    #4 @   #6 @  #4 @ # 6@ #4 @                               MRC  Init    24 hr  20    50   20    50   20   50                             ______________________________________                                        22   108     107    2100   960 2500  1090 3000 1270                           23   114     114    2200  1040 2750  1180 3150 1300                           24   117     118    2550  1140 2950  1220 3150 1300                           25   117     118    2900  1260 3150  1300 3300 1360                           CE4  102      97    3750  1770 5350  2240 6400 2720                           ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                        H.sub.c             SR            SFD                                         MRC     Init   24 hr    Init 24 hrs Init 24 hrs                               ______________________________________                                        22      767    759      0.818                                                                              0.802  0.427                                                                              0.454                                23      764    751      0.822                                                                              0.788  0.427                                                                              0.454                                24      762    747      0.819                                                                              0.794  0.435                                                                              0.458                                25      762    745      0.830                                                                              0.792  0.440                                                                              0.461                                CE 4    759    751      0.813                                                                              0.779  0.441                                                                              0.487                                ______________________________________                                    

The subject matter claimed is:
 1. A polyester which incorporates afunctional group having the formula: ##STR4## wherein R¹ and R² are thesame or different oxyalkyl radicals having from 2 to 8 carbon atoms, R³is an alkylene radical having from 1 to 8 carbon atoms, R⁴ is alkylradical having from 1 to 12 carbon atoms, a cycloalkyl radical havingfrom 5 to 12 carbon atoms, or an aryl radical having from 6 to 12 carbonatoms wherein the aryl radical may contain a halogen atom, a hydroxylgroup, or an amino group, and M is a metal ion or an ammonium ion. 2.The resin of claim 1 wherein R¹ and R² are oxyethylene radicals.
 3. Theresin of claim 1 wherein R³ is a methylene radical.
 4. The resin ofclaim 1 wherein R⁴ is an ethyl radical.